Polluted Runs

If you’ve heard about the effects of pollution on runners before, it was probably in association with Haile Gebrselassie. More than six years after the fact, his decision to forgo the marathon at the 2008 Beijing Olympics due to concerns about the city’s air quality still stands as the most prominent measure taken to protect a runner from pollution. Gebrselassie, who was the world-record holder in the marathon at the time (and would go on to lower his record the following month in Berlin), suffers from asthma attacks, which can be triggered by particulate matter, ground-level ozone, sulfur dioxide and nitrogen oxide—all of which are common in urban air, especially in a city like Beijing. For Gebrselassie, running in such conditions could have resulted in wheezing and coughing, chest pain or even death.

As it turned out, by a combination of drastic action (closing factories and banning over a million cars from the roads in the lead-up to the games) and a fortunate turn in the weather, the race saw better conditions than forecasted. Skies were blue, the air was relatively fresh. Gebrselassie said in an interview that given how conditions were shaping up, he regretted not running—but going in, it wasn’t worth the risk.

Though Gebrselassie’s case is the best-known, this story does not go away. Four years later in London, pollution levels rose to their worst levels in six years in the week before the games, threatening to worsen performances and cause illness among endurance athletes. Again, organizers took action, planning the marathon for the early morning, which helped to avoid high levels of ozone for the race. This story will emerge again in two years in Rio de Janeiro, another highly polluted city.

Unlike Olympic athletes, most of us are not granted the luxury of having major world cities shut down for the sake of our respiratory health. Instead, we must consider the dangers of air pollution for ourselves and plan our running accordingly

Of immediate concern are those effects of pollution that occur midrun. Michael Koehle, a professor in the School of Kinesiology at the University of British Columbia, says athletes can have symptoms such as chest tightness and shortness of breath, which can reduce the ability to get air in and out efficiently.

Ozone (O3), which is produced at ground level when exhaust from cars mixes with direct sunlight, is often responsible for coughing, wheezing, headaches, nausea, and eye and throat irritation. Ozone concentration is highest in the summer and during high-traffic times of the day.

Added to these discomforts, your cardiovascular system is less efficient amid pollution. Carbon monoxide (CO) is the most detrimental pollutant in this respect. It impairs performance by bonding with hemoglobin and preventing oxygen from reaching muscles. In heavy smog, as much as 5 percent of red blood cells can be overwhelmed by carbon monoxide, leaving fewer cells to transport oxygen.

Of more serious concern, however, are the long-term health effects from exposure to air pollution. While ozone and carbon monoxide produce uncomfortable performance-reducing effects, they don’t remain in the body for more than a few hours after exercise, and their effects don’t accrue over time.

Heavy metals and carcinogens, however, cannot be metabolized by the liver and do remain in the body, says Alison Carlisle of the Sport Performance Assessment and Research Centre at Roehampton University in the U.K. She refers to studies in London and South Africa that have shown athletes who train in cities accumulate higher levels of lead in their blood than those who train in rural areas.

The respiratory effects of particulate matter—matter suspended in the atmosphere—can be chronic. Increased particulate concentration leads to more frequent severe respiratory symptoms for asthmatics and nonasthmatics alike. “Individuals with pre-existing respiratory and/or cardiac disorders are at a risk of acute effects from exposure to particles,” Carlisle says. “The effects range from changes in lung function through increased symptoms and days of restricted activity to hospital admission and premature mortality.”

Thankfully, there are ways to mediate exposure to pollutants. The best way to avoid pollution is to choose your running venues carefully. “Consider the geography of a city and its weather patterns as well as its reputation,” Carlisle says. “Some cities, like Los Angeles, are in basins surrounded by mountains, and air pollution becomes trapped, unable to escape to the upper atmosphere. Cities with smog are best to avoid if there is a choice.”

Running away from dense urban areas is not always practical. If you’re stuck running in a smoggy city, here are precautions you can take:

Avoid busy streets and times of days when traffic is heavy. Running before morning rush hour is usually best.

Pay attention to air quality forecasts. AirNow.gov has a color-coded and easy-to-use air-quality index that’s updated in real time. Air quality can be checked at epa.gov and stateoftheair.org.

On days when pollution is particularly high, it might make sense to run indoors on a treadmill where air conditioning is filtering out pollutants.

Runners with asthma, diabetes, heart or lung conditions, or lower respiratory disease should take extra precaution.

Given the risks, you may wonder if running in bad air is even worth it. It’s supposed to improve health, not compromise it. A bit of good news, finally: It turns out the positive effects of running are usually sufficient to outweigh the negative effects of pollution. On average, regular exercise extends life more than increased exposure to pollution shortens it.

“Once you add exercise to the picture, it gets interesting,” Koehle says. “A lot of the health consequences of living in a high-pollution environment are those conditions—such as heart attack and angina—that are reduced with regular exercise. On balance, it appears that people living in a polluted city who exercise will have less health problems than those who do not.”

The negative effects of pollution are overcome by running, but not neutralized by it. Good running is best when you’re breathing clean air.

Scott F. Parker is the author of the memoir Running After Prefontaine, in which he espouses what he calls "the joy of running qua running." He interviewed Thaddeus Kostrubala, author of The Joy of Running, for Running Times in 2011.

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